Update all examples: Z is character 25, not 26

The library examples show the following comment at the beginning:

```cpp
/**
* Encoding "text" as 5 bits characters using the following:
*   A -> 0
*   Z -> 26
*     -> 27
*   . -> 28
*   0 -> 29
*   1 -> 30
*   2 -> 31
*/
```

The chacacter `Z` should be encoded as 25, not 26. Other characters should also be updated to follow the index sequence.